1. Field of the Invention
The present invention relates to an improvement in the wet milling process for separating and recovering products from corn. More particularly, the present invention relates to an improved steeping process which results in improved millability giving higher yields of starch and in a steepwater having a low reducing sugar content.
2. Description of the Related Art
In the usual processing of corn, the whole corn is steeped in water containing sulfur dioxide at an elevated temperature and acid pH for an extended period of time. During the course of the soaking, the soluble substances are extracted from the corn grain to the soaking water where they ferment due to the presence of lactic acid bacteria in the water. Variables such as soaking time, SO.sub.2 levels, water removal rates, temperatures, etc. are used to promote separation. The resulting steepwater is used as a fermentation medium to produce a wide variety of products such as enzymes, pharmaceuticals, etc. Due to the many variations in the process, the quality of corn steepwater found in the market varies widely.
An early description of a simple steeping process is described in U.S. Pat. No. Re. 18,775 where acidulated water is added to a single steep tank. Following separation of the starch, the water is re-used in the process. Other early descriptions of steeping processes involving the recycling of the steepwater back to the process are found in U.S. Pat. Nos. 58,824; 1,655,395; and 1,960,985.
U.S. Pat. No. 2,232,555 describes a process in which corn is soaked in acidified water having a pH of 4.5 to 6.9 at a temperature of 125.degree. F. to 145.degree. F. for about 5 to 15 hours to provide an extract containing substantial quantities of water soluble carbohydrates or sugars.
U.S. Pat. No. 4,359,528 describes a process for producing steepwater having a high amino acid content and useful in the production of penicillin. The process utilizes decreasing temperatures over a series of silos and high cycling ratios of water to corn. A pH of 3.95 to 4.2 is reported.
U.S. Pat. No. 4,980,282 describes a process in which the steepwater is separated from the process, incubated to develop a biomass and the developed biomass treated at a temperature between 40.degree. C. to about 48.degree. C. at a pH of at least about 3.5.
While producing steepwater of varying degrees of usefulness, a process has now been found that provides a steepwater having the low reducing sugar content necessary for use as a fermentation medium while providing high yields of starch.